The disclosure of Japanese Patent Application No. 2000-225923 filed on Jul. 26, 2000 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of the Invention
The invention generally relates to an internal combustion engine mounted on a vehicle and the like. More particularly, the invention relates to an internal combustion engine preheated upon or before starting, and a control method of the same.
2. Description of Related Art
In recent years, an internal combustion engine mounted on an automobile and the like is required to improve startability upon cold starting, reduce fuel consumption, and improve exhaust emission.
In response to these requirements, a heat-accumulating device for the engine as described in JP-A-6-185359 has been proposed. According to the disclosed heat-accumulating device, a water-cooled internal combustion engine includes a first cooling-water passage running through a cylinder block and a second cooling-water passage running through a cylinder head. A heat accumulator is provided in the second cooling-water passage. When the internal combustion engine is cold, the cooling water heated by the heat accumulator is circulated through the second cooling-water passage so as to allow early completion of warm-up of the water passage so as to allow early completion of warm-up of the intake system and fuel supply system by warming the cylinder head first.
Upon cold starting of the internal combustion engine, the fuel is likely to adhere to the wall surface of, for example, an intake port, a combustion chamber and the like because of the low temperature. Therefore, it is known that, when the internal combustion engine is cold, an air-fuel ratio of the engine is reduced taking into account of the amount of the fuel adhering to the wall surface.
In the conventional heat-accumulating device for the engine as described above, however, the air-fuel ratio of the engine is not taken into account in the case of warm-up of the intake system and fuel supply system using hot cooling water stored in a heat-accumulating container. Therefore, the heat-accumulating device may be controlled to reduce the air-fuel ratio despite the fact that the wall-surface temperature of the intake port or combustion chamber has been increased.
If the air-fuel ratio is reduced at a high temperature of the wall surface of the intake port, combustion chamber and the like, a fuel-rich mixture is produced. As a result, a relatively large amount of unburned fuel components is discharged from the internal combustion engine, thereby possibly degrading the exhaust emission.
It is also known that, at a cold starting of an internal combustion engine having spark plugs, for example, a gasoline engine, an exhaust purifying catalyst is not activated yet. Therefore, the ignition timing is retarded to raise the exhaust temperature such that the exhaust purifying catalyst is activated as early as possible. During the cold starting, however, combustion of the air-fuel mixture is likely to be unstable. In this respect, a degree of retarding the ignition timing is limited.
The conventional heat accumulating device for the engine as described above has not taken into account of the ignition timing set for warming up the intake system and fuel supplying system with the hot cooling water stored in the heat accumulating container. Therefore, the degree of retarding the ignition timing may possibly be limited despite the fact that the ignition performance and combustion stability of the air-fuel mixture have been obtained by warming up the intake system and fuel supplying system.
If the degree of retarding the ignition timing is limited when the ignition performance and combustion stability of the air-fuel mixture have been compensated by warming up the intake system and fuel supply system, the exhaust temperature cannot be raised to a desired value. As a result, it may take a long time to activate the exhaust purifying catalyst.
The invention is made in view of the foregoing problems, and it is an object of the invention to prevent degradation in the exhaust emission and to enable early activation of an exhaust purifying catalyst using a technique capable of optimally controlling the air-fuel ratio and/or the ignition timing of the internal combustion engine that is preheated before or upon starting.
In order to solve the aforementioned problems, the invention employs the following apparatus:
An internal combustion engine of the invention is provided with an engine preheating apparatus which preheats the internal combustion engine upon or before starting thereof, and an air-fuel ratio controller which sets an air-fuel ratio of the internal combustion engine that is preheated by the engine preheating apparatus to a value higher than the air-fuel ratio of the internal combustion engine that is not preheated by the engine preheating apparatus.
In this case, the air-fuel ratio of the internal combustion engine that is preheated upon or before starting thereof is set to a value higher than the air-fuel ratio of the internal combustion engine that is not preheated.
In the case where the internal combustion engine is not preheated upon or before starting thereof, the wall surface of an intake air passage, combustion chamber or the like in the internal combustion engine is at a low temperature. Therefore, the fuel is unlikely to be vaporized. So the amount of fuel adhered to the wall surface of the intake air passage, combustion chamber or the like (hereinafter referred to as a fuel adhesion amount) is increased. Meanwhile in the case where the internal combustion engine is preheated upon or before starting thereof, the wall surface of the intake air passage, combustion chamber or the like is at an increased temperature. Therefore, the fuel is likely to be vaporized, reducing the fuel adhesion amount.
In the case where the internal combustion engine is not preheated, the air-fuel ratio has to be reduced by increasing the fuel injection amount as the fuel adhesion amount increases. Meanwhile, in the case where the internal combustion engine is preheated, the fuel adhesion amount is reduced. Accordingly the necessity of reducing the air-fuel ratio by increasing the fuel injection amount is eliminated.
That is, the air-fuel ratio of the internal combustion engine that is preheated upon or before starting thereof is set to a value higher than the air-fuel ratio of the internal combustion engine that is not preheated. The resultant air-fuel ratio is not brought into a fuel-rich state. This makes it possible to prevent excessive unburned fuel components from being discharged from the internal combustion engine.
The air-fuel ratio controller may be constructed to change the air-fuel ratio according to a temperature of the internal combustion engine upon completion of the preheating by the engine preheating apparatus. Such control may be performed on the ground that the fuel adhesion amount strongly correlates with the temperature of the internal combustion engine, that is, the fuel adhesion amount is reduced as the temperature of the internal combustion engine increases.
The temperature of the internal combustion engine may include the wall-surface temperature of the intake air passage, and the wall-surface temperature of the combustion chambers.
An internal combustion engine of the invention is provided with an engine preheating apparatus which preheats the internal combustion engine upon or before starting thereof, and an ignition timing controller which retards an ignition timing of the internal combustion engine that is preheated by the engine preheating apparatus as compared with the ignition timing of the internal combustion engine that is not preheated.
According to such an internal combustion engine, the ignition timing of the internal combustion engine that is preheated upon or before starting thereof is retarded as compared with the internal combustion engine that is not preheated
When the ignition timing is retarded in a cold state of the internal combustion engine, combustion is likely to become unstable owing to degradation in the ignition performance. By preheating the internal combustion engine, the intake air temperature and the compression end temperature increase and accordingly, vaporization of the fuel is facilitated. As a result, the temperature of the air-fuel mixture increases. Therefore, the ignition performance and combustion stability of the mixture are hardly influenced by retardation of the ignition timing.
Moreover, as the ignition timing of the internal combustion engine is retarded, the combustion timing of the mixture is delayed correspondingly. The burned gas at a relatively high temperature is discharged as the exhaust gas from the internal combustion engine immediately after combustion. When the high temperature exhaust gas is discharged from the internal combustion engine, an exhaust purifying catalyst provided in the exhaust passage of the internal combustion engine is heated by the exhaust gas, allowing early activation of the exhaust purifying catalyst.
The ignition-timing controller may be constructed to change a degree of retarding the ignition timing according to a temperature of the internal combustion engine upon completion of the preheating. Such control may be performed on the ground that the ignition performance and combustion stability of the mixture closely correlate with the temperature of the internal combustion engine. That is, the ignition performance and combustion stability of the mixture are improved as the temperature of the internal combustion engine increases.
An internal combustion engine of the invention is provided with an engine preheating apparatus which preheats the internal combustion engine upon or before starting thereof, an air-fuel ratio controller which sets an air-fuel ratio of the internal combustion engine that is preheated by the engine preheating apparatus to a value higher than the air-fuel ratio of the internal combustion engine that is not preheated, and an ignition-timing controller which retards an ignition timing of the internal combustion engine that is preheated as compared with the ignition timing of the internal combustion engine that is not preheated.
In the above case, the air-fuel ratio of the internal combustion engine that is preheated upon or before starting thereof is set to a value higher than the air-fuel ratio of the internal combustion engine that is not preheated. The ignition timing of the internal combustion engine that is preheated upon or before starting thereof is retarded as compared with the internal combustion engine that is not preheated. This makes it possible to prevent the air-fuel ratio from being fuel-rich, and to increase the exhaust gas temperature without deteriorating the combustion stability of the internal combustion engine. As a result, excessive unburned fuel components are not discharged from the internal combustion engine, and the exhaust purifying catalyst can be activated at an earlier stage.
The air-fuel ratio controller and the ignition timing controller may be constructed to change the air-fuel ratio and the degree of retarding the ignition timing, respectively according to a temperature of the internal combustion engine upon completion of the preheating.
The internal combustion engine of the invention may be constructed to further include an intake air amount controller which sets an intake air amount upon preheating of the internal combustion engine to a value larger than the intake air amount of the internal combustion engine that is not preheated.
In this case, combustion energy of the internal combustion engine is increased as the intake air amount increases. Accordingly, unnecessary reduction in the engine speed is reduced even when increasing the air-fuel ratio is increased and/or the degree of retarding the ignition timing are amount of the ignition timing.
The heating medium may include engine coolant, lubricant and the like.